/* 
 * %Z%file      %M% 
 * %Z%author    Sun Microsystems, Inc. 
 * %Z%version   %I% 
 * %Z%date      %D% 
 * 
 * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */ 

package com.sun.jmx.snmp.agent;

// java imports
// 
import java.io.Serializable;
import java.util.Hashtable;
import java.util.Enumeration;
import java.util.Vector;

// jmx imports
//
import com.sun.jmx.snmp.SnmpOid;
import com.sun.jmx.snmp.SnmpValue;
import com.sun.jmx.snmp.SnmpVarBind;
import com.sun.jmx.snmp.SnmpStatusException;

// SNMP Runtime imports
//
import com.sun.jmx.snmp.agent.SnmpMibOid;
import com.sun.jmx.snmp.agent.SnmpMibNode;

/**
 * Represents a node in an SNMP MIB which corresponds to a group.
 * This class allows subnodes to be registered below a group, providing
 * support for nested groups. The subnodes are registered at run time
 * when registering the nested groups in the global MIB OID tree.
 * <P>
 * This class is used by the class generated by <CODE>mibgen</CODE>.
 * You should not need to use this class directly.
 *
 * <p><b>This API is a Sun Microsystems internal API  and is subject 
 * to change without notice.</b></p>
 * @version     4.3     10/29/99
 * @author      Sun Microsystems, Inc
 */

public abstract class SnmpMibGroup extends SnmpMibOid 
    implements Serializable {

    // We will register the OID arcs leading to subgroups in this hashtable.
    // So for each arc in varList, if the arc is also in subgroups, it leads
    // to a subgroup, if it is not in subgroup, it leads either to a table
    // or to a variable.
    protected Hashtable subgroups = null;

    /**
     * Tells whether the given arc identifies a table in this group.
     *
     * @param arc An OID arc.
     *
     * @return <CODE>true</CODE> if `arc' leads to a table.
     */
    public abstract boolean      isTable(long arc);

    /**
     * Tells whether the given arc identifies a variable (scalar object) in 
     * this group.
     *
     * @param arc An OID arc.
     *
     * @return <CODE>true</CODE> if `arc' leads to a variable.
     */
    public abstract boolean      isVariable(long arc);

    /**
     * Tells whether the given arc identifies a readable scalar object in 
     * this group.
     *
     * @param arc An OID arc.
     *
     * @return <CODE>true</CODE> if `arc' leads to a readable variable.
     */
    public abstract boolean      isReadable(long arc);


    /**
     * Gets the table identified by the given `arc'.
     *
     * @param arc An OID arc.
     *
     * @return The <CODE>SnmpMibTable</CODE> identified by `arc', or 
     *    <CODE>null</CODE> if `arc' does not identify any table.
     */
    public abstract SnmpMibTable getTable(long arc);

    /**
     * Checks whether the given OID arc identifies a variable (scalar 
     * object).
     *
     * @exception If the given `arc' does not identify any variable in this
     *    group, throws an SnmpStatusException.
     */
    public void validateVarId(long arc, Object userData) 
	throws SnmpStatusException {
	if (isVariable(arc) == false) 
	    throw noSuchObjectException;
    }
	
	
    // -------------------------------------------------------------------
    // We use a hashtable (subgroup) in order to determine whether an
    // OID arc leads to a subgroup. This implementation can be changed if 
    // needed...
    // For instance, the subclass could provide a generated isNestedArc() 
    // method in which the subgroup OID arcs would be hardcoded.
    // However, the generic approach was prefered because at this time
    // groups and subgroups are dynamically registered in the MIB.
    //
    /**
     * Tell whether the given OID arc identifies a sub-tree
     * leading to a nested SNMP sub-group. This method is used internally.
     * You shouldn't need to call it directly.
     *
     * @param arc An OID arc.
     *
     * @return <CODE>true</CODE> if the given OID arc identifies a subtree
     * leading to a nested SNMP sub-group.
     *
     */
    public boolean isNestedArc(long arc) {
	if (subgroups == null) return false;
	Object obj = subgroups.get(new Long(arc));
        // if the arc is registered in the hashtable, 
	// it leads to a subgroup.
	return (obj != null);
    }

    /**
     * Generic handling of the <CODE>get</CODE> operation.
     * <p>The actual implementation of this method will be generated
     * by mibgen. Usually, this implementation only delegates the
     * job to some other provided runtime class, which knows how to
     * access the MBean. The current toolkit thus provides two 
     * implementations:
     * <ul><li>The standard implementation will directly access the
     *         MBean through a java reference,</li>
     *     <li>The generic implementation will access the MBean through
     *         the MBean server.</li>
     * </ul>
     * <p>Both implementations rely upon specific - and distinct, set of
     * mibgen generated methods.
     * <p> You can override this method if you need to implement some
     * specific policies for minimizing the accesses made to some remote
     * underlying resources.
     * <p>
     *
     * @param req   The sub-request that must be handled by this node.
     *
     * @param depth The depth reached in the OID tree.
     *
     * @exception SnmpStatusException An error occurred while accessing 
     *  the MIB node.
     */
    abstract public void get(SnmpMibSubRequest req, int depth) 
	throws SnmpStatusException;

    /**
     * Generic handling of the <CODE>set</CODE> operation.
     * <p>The actual implementation of this method will be generated
     * by mibgen. Usually, this implementation only delegates the
     * job to some other provided runtime class, which knows how to
     * access the MBean. The current toolkit thus provides two 
     * implementations:
     * <ul><li>The standard implementation will directly access the
     *         MBean through a java reference,</li>
     *     <li>The generic implementation will access the MBean through
     *         the MBean server.</li>
     * </ul>
     * <p>Both implementations rely upon specific - and distinct, set of
     * mibgen generated methods.
     * <p> You can override this method if you need to implement some
     * specific policies for minimizing the accesses made to some remote
     * underlying resources.
     * <p>
     *
     * @param req   The sub-request that must be handled by this node.
     *
     * @param depth The depth reached in the OID tree.
     *
     * @exception SnmpStatusException An error occurred while accessing 
     *  the MIB node.
     */
    abstract public void set(SnmpMibSubRequest req, int depth) 
	throws SnmpStatusException;

    /**
     * Generic handling of the <CODE>check</CODE> operation.
     *
     * <p>The actual implementation of this method will be generated
     * by mibgen. Usually, this implementation only delegates the
     * job to some other provided runtime class, which knows how to
     * access the MBean. The current toolkit thus provides two 
     * implementations:
     * <ul><li>The standard implementation will directly access the
     *         MBean through a java reference,</li>
     *     <li>The generic implementation will access the MBean through
     *         the MBean server.</li>
     * </ul>
     * <p>Both implementations rely upon specific - and distinct, set of
     * mibgen generated methods.
     * <p> You can override this method if you need to implement some
     * specific policies for minimizing the accesses made to some remote
     * underlying resources, or if you need to implement some consistency
     * checks between the different values provided in the varbind list.
     * <p>
     *
     * @param req   The sub-request that must be handled by this node.
     *
     * @param depth The depth reached in the OID tree.
     *
     * @exception SnmpStatusException An error occurred while accessing 
     *  the MIB node.
     */
    abstract public void check(SnmpMibSubRequest req, int depth) 
	throws SnmpStatusException;

    // --------------------------------------------------------------------
    // If we reach this node, we are below the root OID, so we just
    // return.
    // --------------------------------------------------------------------
    public void getRootOid(Vector result) {
	return;
    }

    // -------------------------------------------------------------------
    // PACKAGE METHODS
    // -------------------------------------------------------------------
    
    // -------------------------------------------------------------------
    // This method can also be overriden in a subclass to provide a 
    // different implementation of the isNestedArc() method.
    // => if isNestedArc() is hardcoded, then registerSubArc() becomes
    //    useless and can become empty.
    /**
     * Register an OID arc that identifies a sub-tree
     * leading to a nested SNMP sub-group. This method is used internally.
     * You shouldn't ever call it directly.
     *
     * @param arc An OID arc.
     *
     */
    void registerNestedArc(long arc) {
	Long obj = new Long(arc);
	if (subgroups == null) subgroups = new Hashtable();
        // registers the arc in the hashtable.
	subgroups.put(obj,obj);
    }

    // -------------------------------------------------------------------
    // The SnmpMibOid algorithm relies on the fact that for every arc 
    // registered in varList, there is a corresponding node at the same 
    // position in children.
    // So the trick is to register a null node in children for each variable
    // in varList, so that the real subgroup nodes can be inserted at the 
    // correct location. 
    // registerObject() should be called for each scalar object and each 
    // table arc by the generated subclass.
    /**
     * Register an OID arc that identifies a scalar object or a table.
     * This method is used internally. You shouldn't ever call it directly.
     *
     * @param arc An OID arc.
     *
     */
    protected void registerObject(long arc) 
	throws IllegalAccessException {

        // this will register the variable in both varList and children
        // The node registered in children will be null, so that the parent
        // algorithm will behave as if no node were registered. This is a
        // trick that makes the parent algorithm behave as if only subgroups
        // were registered in varList and children.
	long[] oid = new long[1];
	oid[0] = arc;
	super.registerNode(oid,0,null);
    }

    // -------------------------------------------------------------------
    // registerNode() will be called at runtime when nested groups are
    // registered in the MIB. So we do know that this method will only
    // be called to register nested-groups.
    // We trap registerNode() in order to call registerSubArc()
    /**
     * Register a child node of this node in the OID tree.
     * This method is used internally. You shouldn't ever call it directly.
     *
     * @param oid The oid of the node being registered.
     * @param cursor The position reached in the oid.
     * @param node The node being registered.
     *
     */
    void registerNode(long[] oid, int cursor ,SnmpMibNode node) 
	throws IllegalAccessException {
	super.registerNode(oid,cursor,node);
	if (cursor < 0) return;
	if (cursor >= oid.length) return;
        // if we get here, then it means we are registering a subgroup.
        // We will thus register the sub arc in the subgroups hashtable.
	registerNestedArc(oid[cursor]);
    }
    
    // -------------------------------------------------------------------
    // see comments in SnmpMibNode
    // -------------------------------------------------------------------
    void findHandlingNode(SnmpVarBind varbind, 
			  long[] oid, int depth, 
			  SnmpRequestTree handlers) 
	throws SnmpStatusException {

	int length = oid.length;
	SnmpMibNode node = null;
	
	if (handlers == null)
            throw new SnmpStatusException(SnmpStatusException.snmpRspGenErr);

	final Object data = handlers.getUserData();

	if (depth >= length) {
	    // Nothing is left... the oid is not valid
            throw new SnmpStatusException(SnmpStatusException.noAccess);
	}

	long arc = oid[depth];

	if (isNestedArc(arc)) {
	    // This arc leads to a subgroup: delegates the search to the
	    // method defined in SnmpMibOid
	    super.findHandlingNode(varbind,oid,depth,handlers);
	    return;
	} else if (isTable(arc)) {
	    // This arc leads to a table: forward the search to the table.
	    
	    // Gets the table
	    SnmpMibTable table = getTable(arc);
	    
	    // Forward the search to the table
	    table.findHandlingNode(varbind,oid,depth+1,handlers);

	} else {
	    // If it's not a variable, throws an exception
	    validateVarId(arc, data);

	    // The trailing .0 is missing in the OID
	    if (depth+2 > length)
		throw noSuchInstanceException;

	    // There are too many arcs left in the OID (there should remain
	    // a single trailing .0)
	    if (depth+2 < length)
		throw noSuchInstanceException;

	    // The last trailing arc is not .0
	    if (oid[depth+1] != 0L) 
		throw noSuchInstanceException;

	    // It's one of our variable, register this node.
	    handlers.add(this,depth,varbind);
	}
    }

    // -------------------------------------------------------------------
    // See comments in SnmpMibNode.
    // -------------------------------------------------------------------
    long[] findNextHandlingNode(SnmpVarBind varbind, 
				long[] oid, int pos, int depth, 
				SnmpRequestTree handlers, AcmChecker checker) 
	throws SnmpStatusException {
	
	int length = oid.length;
	SnmpMibNode node = null;
	
	if (handlers == null)
	    // This should be considered as a genErr, but we do not want to
	    // abort the whole request, so we're going to throw
	    // a noSuchObject...
	    //
            throw noSuchObjectException;

	final Object data = handlers.getUserData();
	final int pduVersion = handlers.getRequestPduVersion();


	// The generic case where the end of the OID has been reached is
	// handled in the superclass
        // XXX Revisit: this works but it is somewhat convoluted. Just setting
        //              arc to -1 would work too.
	if (pos >= length) 
	    return super.findNextHandlingNode(varbind,oid,pos,depth,
					      handlers, checker);

	// Ok, we've got the arc.
	long arc = oid[pos];

	long[] result = null;

	// We have a recursive logic. Should we have a loop instead?
	try {

	    if (isTable(arc)) {
		// If the arc identifies a table, then we need to forward
		// the search to the table.

		// Gets the table identified by `arc'
		SnmpMibTable table = getTable(arc);

		// Forward to the table
		checker.add(depth, arc);
		try {
		    result = table.findNextHandlingNode(varbind,oid,pos+1,
							depth+1,handlers,
							checker);
		}catch(SnmpStatusException ex) {
		    throw noSuchObjectException;
		} finally {
		    checker.remove(depth);
		}
		// Build up the leaf OID
		result[depth] = arc;
		return result;
	    } else if (isReadable(arc)) {
		// If the arc identifies a readable variable, then two cases:

		if (pos == (length - 1)) {
		    // The end of the OID is reached, so we return the leaf
		    // corresponding to the variable identified by `arc'

		    // Build up the OID
		    // result = new SnmpOid(0);
		    // result.insert((int)arc);
		    result = new long[depth+2];
		    result[depth+1] = 0L;
		    result[depth] = arc;

		    checker.add(depth, result, depth, 2);
		    try {
			checker.checkCurrentOid();
		    } catch(SnmpStatusException e) {
			throw noSuchObjectException;
		    } finally {
			checker.remove(depth,2);
		    }
		    
		    // Registers this node
		    handlers.add(this,depth,varbind);
		    return result;
		} 

		// The end of the OID is not yet reached, so we must return
		// the next leaf following the variable identified by `arc'.
		// We cannot return the variable because whatever follows in
		// the OID will be greater or equals to 0, and 0 identifies
		// the variable itself - so we have indeed to return the 
		// next object. 
		// So we do nothing, because this case is handled at the 
		// end of the if ... else if ... else ... block.

	    } else if (isNestedArc(arc)) {
		// Now if the arc leads to a subgroup, we delegate the 
		// search to the child, just as done in SnmpMibNode. 
		// 
  
		// get the child ( = nested arc node). 
		// 
		final SnmpMibNode child = getChild(arc); 
		
		if (child != null) { 
		    checker.add(depth, arc); 
		    try { 
			result = child.findNextHandlingNode(varbind,oid,pos+1, 
							    depth+1,handlers,  
							    checker); 
			result[depth] = arc; 
			return result;
		    } finally {
			checker.remove(depth);
		    }
		}
	    }
	    
	    // The oid is not valid, we will throw an exception in order
	    // to try with the next valid identifier...
	    //
	    throw noSuchObjectException;

	} catch (SnmpStatusException e) {
	    // We didn't find anything at the given arc, so we're going
	    // to try with the next valid arc
	    //
	    long[] newOid = new long[1];
	    newOid[0] = getNextVarId(arc,data,pduVersion);
	    return findNextHandlingNode(varbind,newOid,0,depth,
					handlers,checker);
	}
    }

}
